Data Sheet

PRECHARGE CCFAST
CHARGE
CVTAPER DONETHERMAL
REGULATION
BatteryVoltage
BatteryCurrent
HI-z
ICJunctionTemperature,T
J
V
O(REG)
I
O(CHG)
V
(LOWV)
I
(PRECHG)
I
(TERM)
T
J(REG)
bq24072 , bq24073 , bq24074 , bq24075 , bq24079
www.ti.com SLUS810K –SEPTEMBER 2008–REVISED MARCH 2015
Note that this feature monitors the die temperature of the bq2407x. This is not synonymous with ambient
temperature. Self heating exists due to the power dissipated in the IC because of the linear nature of the battery
charging algorithm and the LDO associated with OUT. A modified charge cycle with the thermal loop active is
shown in Figure 23. Battery termination is disabled during thermal regulation.
Figure 23. Charge Cycle Modified by Thermal Loop
9.3.6 Battery Pack Temperature Monitoring
The bq2407x features an external battery pack temperature monitoring input. The TS input connects to the NTC
thermistor in the battery pack to monitor battery temperature and prevent dangerous over-temperature
conditions. During charging, I
NTC
is sourced to TS and the voltage at TS is continuously monitored. If, at any
time, the voltage at TS is outside of the operating range (V
COLD
to V
HOT
), charging is suspended. The timers
maintain their values but suspend counting. When the voltage measured at TS returns to within the operation
window, charging is resumed and the timers continue counting. When charging is suspended due to a battery
pack temperature fault, the CHG pin remains low and continues to indicate charging.
For the bq24072 and bq24073, battery pack temperature sensing is disabled when termination is disabled (TD =
High) and the voltage at TS is greater than V
DIS(TS)
. For applications that do not require the TS monitoring
function, connect a 10-kΩ resistor from TS to VSS to set the TS voltage at a valid level and maintain charging.
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Product Folder Links: bq24072 bq24073 bq24074 bq24075 bq24079